Q: Some whales have an underdeveloped hipbone. The hip bone is present in the anatomy but does not have any particular function in the whales' locomotion.
The presence of this vestigial hip bone in a

whale suggests that
A. the same homologous structure may be found in humans.
B. a mutation in the whales' DNA caused the formation of a useless skeletal structure.
C. the whales may acquire the ability to live on land before the end of their lifetime.
D. the hip bone may have played an important role in the whales' ancestors locomotion.

A: The answer to that question is probably D. the hip bone may have played an important role in the whales' ancestors locomotion. [ The presence of a vestigial organ suggests a shared ancestry with another organism that has similar, but functional organs.
The "theory of natural selection" offers a proposed mechanism by which vestigial organs can come about. That is, the existence of vestigial

organs may be hypothesized as resulting from changes in the environment and behavior patterns of the species in question. As the function of the structure is no longer beneficial for survival, the likelihood that future offspring will inherit the "normal" form of the structure decreases. target=_blank rel='nofollow'>http://webcache.googleusercontent.com/search?q=cache:589KtlX_4MYJ:' target=_blank rel='nofollow'>www.newworldencyclopedia.org/entry/Vestigial_organ+presence+of+this+vestigial+hip+bone+in+a+whale+suggests&cd=1&hl=en&ct=clnk&source=www.google.com ]